Brazilian police tipped off by the FBI detained a citizen of Arab origin for three weeks for inciting anti-American hatred on the Internet but released him after finding no evidence of links to a militant group, a federal prosecutor said on Tuesday.

Folha de Sao Paulo, Brazil's largest daily newspaper, earlier reported the man was suspected of being an al Qaeda communications operative.

The federal prosecutor in the financial hub Sao Paulo, where the arrest was made in April, released a statement on Tuesday night saying police had received information from the FBI about a closed Internet group in Arabic that was inciting hatred against Americans.

Police found the suspect was the moderator of the group, which the statement said they suspected could have been linked to a terrorist group.

But the prosecutor, Ana Leticia Absy, added there was no sign the suspect had been planning a terrorist act and that, after 21 days, police had decided they could no longer hold him. No weapons or suspect documents were found.

Federal police said earlier in a statement that a foreign resident in Brazil had been arrested on April 26 for spreading racist content on the Internet using a social networking site.

Asked about the report at a news conference, President Luiz Inacio Lula da Silva said on Tuesday afternoon it appeared police had received allegations against the suspect from outside Brazil.

"We still have no conclusion to accuse the person for whatever it may be," Lula said in the northeastern city of Salvador, adding he had been briefed on the case.

Brazil is home to one of the largest Arab populations outside the Middle East, with most residing in Sao Paulo and Foz do Iguacu, a bustling commercial hub on the border with Argentina and Paraguay.

The U.S. government has claimed that Arabs in the area around Foz do Iguacu raise money for militant groups in the Middle East. Brazil has repeatedly denied the claim, calling it unfounded.